共查询到20条相似文献,搜索用时 24 毫秒
1.
The relations between the kernels, as well as the cokernels, of Toeplitz operators are studied in connection with certain relations between their symbols. These results are used to obtain some Fredholm type properties for operators with 2×2 symbols, whose determinant admits a bounded Wiener-Hopf factorization. 相似文献
2.
Victor Adukov 《Integral Equations and Operator Theory》1993,16(3):305-332
In the paper Wiener-Hopf operators on a semigroup of nonnegative elements of a linearly quasi-ordered torsion free Abelian group are considered. Wiener-Hopf factorization of an invertible element of the group algebra is constructed, notions of a topological index and a factor index are introduced. It turns out that the set of factor indices for invertible elements of the group algebra is a linearly ordered group. It is shown that Wiener-Hopf operator with an invertible symbol is an one-side invertible operator and its invertibility properties are defined by the sign of the factor index of its symbol. Groups on which there exist nontrivial Fredholm Wiener-Hopf operators are described. As an example, all linear quasi-orders on the group n are found and corresponding Wiener-Hopf operators are considered. 相似文献
3.
This note concerns a class of Wiener-Hopf operators on a finite interval, acting between Sobolev multi-index spaces. Necessary and sufficient conditions for such an operator to be Fredholm are given, as well as a formula for the index. The argument is based on a reduction procedure of convolution operators on a finite interval to operators of the same type on the half-line.supported by the Netherlands organization for scientific research (NWO)supported in part by NSF Grant 9101143 相似文献
4.
A.P. Nolasco 《Journal of Mathematical Analysis and Applications》2007,331(1):329-341
This paper presents a Duduchava-Saginashvili's type theory for Wiener-Hopf plus Hankel operators with semi-almost periodic Fourier symbols and acting between Lp Lebesgue spaces. This means the obtainment of one-sided invertibility and Fredholm property for these operators upon certain mean values of the representatives at infinity of their Fourier symbols. Additionally, a formula for the Fredholm index is provided by introducing a corresponding winding number of some new elements. 相似文献
5.
The Fredholm properties (index, kernel, image, etc.) of Wiener-Hopf integral operators are described in terms of realization of the symbol for a class of matrix symbols that are analytic on the real line but not at infinity. The realizations are given in terms of exponentially dichotomous operators. The results obtained give a complete analogue of the earlier results for rational symbols. 相似文献
6.
Leiba Rodman Ilya M. Spitkovsky Hugo J. Woerdeman 《Proceedings of the American Mathematical Society》2002,130(5):1365-1370
We consider Toeplitz operators with symbols that are almost periodic matrix functions of several variables. It is shown that under certain conditions on the group generated by the Fourier support of the symbol, a Toeplitz operator is Fredholm if and only if it is invertible.
7.
Fredholm criteria and index formulas are established for Wiener-Hopf operators W(a) with semi-almost periodic matrix symbols a on weighted Lebesgue spaces where 1 < p < ∞, w belongs to a subclass of Muckenhoupt weights and . We also study the invertibility of Wiener-Hopf operators with almost periodic matrix symbols on . In the case N = 1 we also obtain a semi-Fredholm criterion for Wiener-Hopf operators with semi-almost periodic symbols and, for another
subclass of weights, a Fredholm criterion for Wiener-Hopf operators with semi-periodic symbols.
Work was supported by the SEP-CONACYT Project No. 25564 (México). The second author was also sponsored by the CONACYT scholarship
No. 163480. 相似文献
8.
We study non-elliptic quadratic differential operators. Quadratic differential operators are non-selfadjoint operators defined
in the Weyl quantization by complex-valued quadratic symbols. When the real part of their Weyl symbols is a non-positive quadratic
form, we point out the existence of a particular linear subspace in the phase space intrinsically associated to their Weyl
symbols, called a singular space, such that when the singular space has a symplectic structure, the associated heat semigroup
is smoothing in every direction of its symplectic orthogonal space. When the Weyl symbol of such an operator is elliptic on
the singular space, this space is always symplectic and we prove that the spectrum of the operator is discrete and can be
described as in the case of global ellipticity. We also describe the large time behavior of contraction semigroups generated
by these operators. 相似文献
9.
We consider quasicomplexes of Boutet de Monvel operators in Sobolev spaces on a smooth compact manifold with boundary. To each quasicomplex we associate two complexes of symbols. One complex is defined on the cotangent bundle of the manifold and the other on that of the boundary. The quasicomplex is elliptic if these symbol complexes are exact away from the zero sections. We prove that elliptic quasicomplexes are Fredholm. As a consequence of this result we deduce that a compatibility complex for an overdetermined elliptic boundary problem operator is also Fredholm. Moreover, we introduce the Euler characteristic for elliptic quasicomplexes of Boutet de Monvel operators. 相似文献
10.
V. V. Peller 《Journal of the American Mathematical Society》1998,11(4):751-770
We study maximizing vectors of Hankel operators with matrix-valued symbols. This study leads to a solution of the so-called recovery problem for unitary-valued functions and to a new approach to Wiener-Hopf factorizations for functions in a function space satisfying natural conditions. Finally, we improve earlier results of Peller and Young on hereditary properties of the operator of superoptimal approximation by analytic matrix functions.
11.
We study the composition of time-frequency localization operators (wavepacket operators) and develop a symbolic calculus of
such operators on modulation spaces. The use of time-frequency methods (phase space methods) allows the use of rough symbols
of ultra-rapid growth in place of smooth symbols in the standard classes. As the main application it is shown that, in general,
a localization operator possesses the Fredholm property, and thus its range is closed in the target space. 相似文献
12.
Alexander Alldridge 《Journal of Functional Analysis》2007,249(2):425-453
We study multivariate generalisations of the classical Wiener-Hopf algebra, which is the C∗-algebra generated by the Wiener-Hopf operators, given by convolutions restricted to convex cones. By the work of Muhly and Renault, this C∗-algebra is known to be isomorphic to the reduced C∗-algebra of a certain restricted action groupoid, given by the action of Euclidean space on a certain compactification. Using groupoid methods, we construct composition series for the Wiener-Hopf C∗-algebra by a detailed study of this compactification. We compute the spectrum, and express homomorphisms in K-theory induced by the symbol maps which arise by the subquotients of the composition series in analytical terms. Namely, these symbols maps turn out to be given by an analytical family index of a continuous family of Fredholm operators. In a subsequent paper, we also obtain a topological expression of these indices. 相似文献
13.
L.P. Castro 《Applicable analysis》2013,92(3-4):393-412
We construct an operator relation between convolution type operators with or without a reflection on a union of finite intervals and corresponding Wiener-Hopf operators. This relation is the reult for several other relations between intermediate operators constructed for that purpose. The presented relations are obtained with the help of different extension methods that annulate particular actions of the related operators. All the operators are defined in Bessel potential spaces or Sobolev spaces. In particular, the final relation enables us to derive properties from a Wiener-Hopf operator to the intial one. An example of application of the presented results is done in a differaction problem by a union of two strips 相似文献
14.
Torsten Ehrhardt 《Journal of Functional Analysis》2004,208(1):64-106
It is well known that a Toeplitz operator is invertible if and only if its symbols admits a canonical Wiener-Hopf factorization, where the factors satisfy certain conditions. A similar result holds also for singular integral operators. More generally, the dimension of the kernel and cokernel of Toeplitz or singular integral operators which and Fredholm operators can be expressed in terms of the partial indices of an associated Wiener-Hopf factorization problem.In this paper we establish corresponding results for Toeplitz plus Hankel operators and singular integral operators with flip under the assumption that the generating functions are sufficiently smooth (e.g., Hölder continuous). We are led to a slightly different factorization problem, in which pairs , instead of the partial indices appear. These pairs provide the relevant information about the dimension of the kernel and cokernel and thus answer the invertibility problem. 相似文献
15.
The study of a class of operators associated with convolution equations of the first kind on a finite interval is reduced to the study of Wiener-Hopf operators with piecewise continuous symbol on R. Fredholm properties and invertibility conditions for this class of operators are investigated. An example from diffraction theory is considered.Sponsored by J.N.I.C.T. (Portugal) under grant n
o
87422/MATM. 相似文献
16.
Marek Rakowski 《Journal of Functional Analysis》1992,110(2)
The properties of a discrete Wiener-Hopf equation are closely related to the factorization of the symbol of the equation. We give a necessary and sufficient condition for existence of a canonical Wiener-Hopf factorization of a possibly nonregular rational matrix function W relative to a contour which is a positively oriented boundary of a region in the finite complex plane. The condition involves decomposition of the state space in a minimal realization of W and, if it is satisfied, we give explicit formulas for the factors. The results are generalized by means of centered realizations to arbitrary rational matrix functions. The proposed approach can be used to solve discrete Wiener-Hopf equations whose symbols are rational matrix functions which admit canonical factorization relative to the unit circle. 相似文献
17.
A. Böttcher S. Grudsky I. Spitkovsky 《Journal of Fourier Analysis and Applications》2001,7(5):523-535
It is well known that amplitude modulation does not affect Fredholmness of Toeplitz operators. The same is true for frequency
modulation provided the symbol of the operator is piecewise continuous. In this article, it is shown that frequency modulation
can destroy Fredholmness for Toeplitz operators with almost periodic symbols; the corresponding example is based on the observation
that certain almost periodic functions become semi-almost periodic functions after appropriate frequency modulation. Moreover,
this article contains several results that can be employed in order to decide whether a Toeplitz operator with a frequency
modulated semi-almost periodic symbol is Fredholm. 相似文献
18.
Birgit Jacob 《Mathematische Nachrichten》2001,227(1):81-97
This paper is concerned with Fredholm operator valued Hp – functions on the unit disc, where the Fredholm operators action a Banach space. Sufficient conditions are presented which guarantee that Fatou's theorem is valid. Using the theory of traces and determinants on quasi – Banach operator ideals, we develop conditions that guarantee that the zeros of Fredholm operator valued Hp – functions satisfy the Blaschke condition. 相似文献
19.
By replacement in the definition of the convolution operator of Fourier transform by a spectral transform of a selfadjoint Sturm-Liouville operator on the axis L, the concepts of Lconvolution and L-Wiener-Hopf operators are introduced. The case of the reflectorless potentials with a single eigenvalue is considered. A relationship between the Wiener-Hopf and L-Wiener- Hopf operators is established. In the case of piecewise continuous symbol the Fredholm property and invertibility of the L-Wiener-Hopf operator are investigated. 相似文献
20.
We revisit the computation of (2-modified) Fredholm determinants
for operators with matrix-valued semi-separable integral kernels. The latter
occur, for instance, in the form of Greens functions associated with closed
ordinary differential operators on arbitrary intervals on the real line. Our
approach determines the (2-modified) Fredholm determinants in terms of solutions
of closely associated Volterra integral equations, and as a result offers
a natural way to compute such determinants.We illustrate our approach by identifying classical objects such as the
Jost function for half-line Schrödinger operators and the inverse transmission
coe.cient for Schrödinger operators on the real line as Fredholm determinants,
and rederiving the well-known expressions for them in due course.
We also apply our formalism to Floquet theory of Schrödinger operators, and
upon identifying the connection between the Floquet discriminant and underlying
Fredholm determinants, we derive new representations of the Floquet
discriminant.Finally, we rederive the explicit formula for the 2-modified Fredholm
determinant corresponding to a convolution integral operator, whose kernel
is associated with a symbol given by a rational function, in a straghtforward
manner. This determinant formula represents a Wiener-Hopf analog of Days
formula for the determinant associated with finite Toeplitz matrices generated
by the Laurent expansion of a rational function. 相似文献